Aspects of the present invention are directed to an in-line characterization with temperature profiling.
Reliable in-line characterization is becoming increasingly critical in the development of new technologies and in product manufacturing. At least one reason for this is that certain reliability degradation mechanisms are relatively sensitive to the choice of manufacturing processes to be employed and the materials used in the processes. Degradation mechanisms leading to bias temperature instability (BTI) are examples of these and are key reliability concerns in at least advanced integrated circuit (IC) technologies.
Accurate in-line BTI testing is not generally possible, however, due to the tendencies for devices under test conditions to recover from applied stress relatively quickly (i.e., fast recovery) after a point, such as the beginning of a test, where the stress is no longer applied. The tendency for devices to recover quickly is a particular concern at elevated stress temperatures. In these cases, negative-bias-temperature-instability (NBTI) in p-channel metal oxide semiconductor field-effect transistors (PMOSFETs) typically consists of two degradation mechanisms, which include, for example, interface-state generation between a channel (Si) and gate dielectrics (such as SiO2). Interface-state generation is a thermally activated process that degrades the device and circuit performance.
It has been observed that the NBTI-shift due to interface-state generation recovers quickly during device tests after the stress bias is removed. Special high-speed instruments are needed in order to capture the real degradation before recovery occurs. The use of such instruments is generally impractical in production environments.